We present a collection of 100 vertical component seismograms of a Kuril Islands earthquake recorded by stations in western Europe (between 73 and 95¿ of epicentral distance) which shows evidence of a PdP wave reflected on top of D″ beneath northern Siberia. The PdP travel time curve varies rapidly, suggesting the existence of sharp lateral variations (scale length smaller than 1¿). The first onset times observed at distances larger than 85¿ are compatible with a D″ velocity about 1% larger than standard models along these paths, up to a depth of 2850 km. By one dimensional forward modeling we find one model with a 2.8% discontinuity at 2605 km depth, another with a 7 km thick 3% low velocity lamella at 2607 km depth. They both generate waveforms which fit the data similarly. ¿ 1999 American Geophysical Union